TY - JOUR T1 - Happens in the best of subfamilies: Replacement and internalisation of co-obligate <em>Serratia</em> endosymbionts in Lachninae aphids JF - bioRxiv DO - 10.1101/059816 SP - 059816 AU - Alejandro Manzano-Marín AU - Gitta Szabo AU - Jean-Christophe Simon AU - Matthias Horn AU - Amparo Latorre Y1 - 2016/01/01 UR - http://biorxiv.org/content/early/2016/06/19/059816.abstract N2 - Virtually all aphids maintain an obligate mutualistic symbiosis with bacteria from the Buchnera, genus, which produce essential nutrients for their aphid hosts. Most aphids from the Lachninae subfamily have been consistently found to house additional endosymbionts, mainly Serratia symbiotica. This apparent dependence on secondary endosymbionts was proposed to have been triggered by the loss of the riboflavin biosynthetic capability by Buchnera in the Lachninae last common ancestor. However, an integral large-scale analysis of secondary endosymbionts in the Lachninae is still missing, hampering the interpretation of the evolutionary and genomic analyses of these endosymbionts. Here, we analysed the endosymbionts of selected representatives from seven different Lachninae genera and nineteen species, spanning four tribes, both by FISH (exploring the symbionts’ morphology and tissue tropism) and 16S rRNA gene sequencing. We demonstrate that all analysed aphids possess dual symbiotic systems, and while most harbour S. symbiotica, some have undergone symbiont replacement by other phylogenetically-distinct bacterial taxa. We found that these secondary associates display contrasting cell shapes and tissue tropism, and some appear to be lineage-specific. We propose a scenario for symbiont establishment in the Lachninae, followed by independent internalisations into bacteriocytes and symbiont replacement events, thereby highlighting the extraordinary versatility of host-symbiont interactions. ER -